NCERT Solutions for Class 12 Biology Chapter 12: Biotechnology and its Application

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    1. Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because:
    (a) bacteria are resistant to the toxin.
    (b) toxin is immature.
    (c) toxin is inactive.
    (d) bacteria encloses toxin in a special sac.

    Ans. (c) toxin is inactive.

    2. What are transgenic bacteria? Illustrate using any one example

    Ans. Transgenic bacteria are the genetically modified bacteria that carry the gene from other sources and are used for the production of desired gene product at large scale.
    An example of transgenic bacteria is E.coli. In the plasmid of E.coli, the two DNA sequences corresponding to A and B chains of human insulin are inserted. Hence, after insertion of insulin gene into bacterium, it becomes transgenic and start producing human insulin.

    3. Compare and contrast the advantages and disadvantages of production of genetically modified crops.

    Ans. Advantages of producing genetically modified crops are as:
    (i) It becomes more tolerate to environmental factors.
    (ii) It enhances the yield of crop.
    (iii) They are more resistant to plant pathogens.
    (iv) They have increased nutritional and yield.
    (v) More amount of crop can be grown in less area.
    Disadvantages of producing genetically modified crops are as:
    (i) They can affect the native biodiversity in an area.
    (ii) They can use genetic pollution an coiled relative of crop plant hence it is affecting our natural environment.
    (iii) They are affecting human health.

    4. What are Cry proteins? Name an organism that produces it. How has man exploited this protein to his benefit?

    Ans. Cry proteins: It is a toxic crystal protein encoded by cry gene which is toxic to certain insects. Cry protein is produced by a Bacteria named Bacillus thuringiensis.
    Human are taking advantage by incorporating cry gene in crops to form transgenic crop which are insect resistant e.g., BT cotton.

    5. What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.

    Ans. Gene therapy is technique for correction of defective gene by repairing or adding correct copy. ADA (adenosine deaminase deficiency) is a very rare genetic disorder due to deletion of the gene for adenosine deaminase. The enzyme is crucial for the immune system to functions. It can be treated by gene therapy. This gene is transferred into early embryonic cells of bone marrow for permanent use.

    6. Diagrammatically represent the experimental steps in cloning and expressing an human gene (say the gene for growth hormone) into a bacterium like E. coli?

    human gene

    7. Can you suggest a method to remove oil (hydrocarbon) from seeds based on your understanding of rDNA technology and chemistry of oil?

    Ans. Glycerols and fatty acids are main components of seed oils. Insertion of recombinant DNA carrying the gene of any inhibitor of oil synthesis will inhibit the synthesis of oil in seed. Thus recombinant seeds would not have oil.
    Removing of gene responsible for the synthesis of oil is another option.

    8. Find out from internet what is golden rice.

    Ans. Golden rice is a transgenic variety of rice (Oryza sativa) containing good quantities of b-carotene (provitamin A) which is principle source of vitamin A. Since the grains of the rice are yellow in colour due to b-carotene, the rice is commonly called golden rice. It was developed at Swiss Federal Institute of Technology by Professor Ingo Potrykus and Peter Beyer.

    9. Does our blood have proteases and nucleases?

    Ans. No, human blood does not have protease and nucleases because blood serum contains different types of protease inhibitors.

    10. Consult internet and find out how to make orally active and protein pharmaceutical. What is the major problem to be encountered?

    Ans. Orally active protein product that is successfully manufactured is vaccines for preventions of infectious diseases such as hepatitis B, herpes, influenza, etc. Gene for antigen are isolated from bacteria and grown along with cut leaf portions of potato plant in antibiotic medium – followed by callus formation and recombinant/transgenic potato are obtained which contain those vaccines.

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